Multiple Input-Multiple Output Cycle-to-Cycle Control of Manufacturing Processes

Cycle-to-cycle control is a method for using feedback to improve product quality for processes that are inaccessible within a single processing cycle. This limitation stems from the impossibility or the prohibitively high cost of placing sensors and actuators that could facilitate control during, or within, the process cycle. Our previous work introduced cycle to cycle control for single input-single output systems, and here it is extended to multiple input-multiple output systems. Gain selection, stability, and process noise amplification results are developed and compared with those obtained by previous researchers, showing good agreement. The limitation of imperfect knowledge of the plant model is then imposed. This is consistent with manufacturing environments where the cost and number of tests to determine a valid process model is desired to be minimal. The implications of this limitation are modes of response that are hidden from the controller. Their effects on system performance and stability are discussed.Singapore-MIT Alliance (SMA

Process Control in Micro-Embossing: A Review

Abstract— A promising technique for the large-scale manufacture of micro-fluidic devices and photonic devices is hot embossing of polymers such as PMMA. Micro-embossing is a deformation process where the workpiece material is heated to permit easier material flow and then forced over a planar patterned tool. In this work we review the basic process and the state of research with respect to manufacturing process control, where the latter is defined as methods for minimizing variation in the product while maximizing production rate. From this review we conclude the following: Several investigators have reported success at creating micron scale features using this process, but none have performed a formal characterization or optimization of the process.Singapore-MIT Alliance (SMA

Cyclotron resonance in the layered perovskite superconductor Sr2RuO4

We report a detailed study of the magnetic-field-orientation dependence of the millimetre-wave magnetoconductivity of the superconductor Sr2RuO4 We find two harmonic series of cyclotron resonances. We assign the first, corresponding to a quasiparticle mass of $4.29 \pm 0.05 m_{\rm e}$, where $m_{\rm e}$ is the free-electron mass, to the $\beta$ Fermi-surface section. We assign the second series, which contains only odd harmonics, to cyclotron resonance of the $\gamma$ Fermi-surface section, yielding a quasiparticle mass of $12.35 \pm 0.20 m_{\rm e}$. A third, single cyclotron resonance, corresponding to a quasiparticle mass of $5.60 \pm 0.03 m_{\rm e}$, is attributed to the $\alpha$ Fermi-surface section. In addition, we find a very strong absorption mode in the presence of a magnetic field component parallel to the quasi-two-dimensional planes of the sample. Its dependence on the orientation of the magnetic field cannot be described in the context of conventional cyclotron resonance, and the origin of this mode is not yet clear.Comment: Submitted to J. Phys. Cond. Ma

Low temperature electronic properties of Sr_2RuO_4 II: Superconductivity

The body centered tetragonal structure of Sr_2RuO_4 gives rise to umklapp scattering enhanced inter-plane pair correlations in the d_{yz} and d_{zx} orbitals. Based on symmetry arguments, Hund's rule coupling, and a bosonized description of the in-plane electron correlations the superconducting order parameter is found to be a orbital-singlet spin-triplet with two spatial components. The spatial anisotropy is 7%. The different components of the order parameter give rise to two-dimensional gapless fluctuations. The phase transition is of third order. The temperature dependence of the pair density, specific heat, NQR, Knight shift, and susceptibility are in agreement with experimental results.Comment: 20 pages REVTEX, 3 figure

Millimetre-wave magneto-optical studies of systems with reduced dimensionality

branches are found, which arise from the complicated nature of the band dispersion in this metal. In Chapter 5, a resonant absorption of microwaves is observed in the superconducting state of kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2 and interpreted as a Josephson Plasma Resonance. The superconducting to normal transition is studied as a function of temperature and provides information about the temperature dependence of the upper critical field in kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2. Chapter 6 presents measurements of electron paramagnetic resonance in the quasi-two dimensional Heisenberg antiferromagnet Cs sub 2 CuCl sub 4. The evolution of the magnetic resonance absorption between the high temperature region (the paramagnetic regime) and temperatures below T sub N (the antiferromagnetic regime), is studied for a range of crystal orientations. At temperatures considerably higher than T sub N , the magneto-optical data show the onset of short-range spin correlations. Experimental studies of the magneto-optical response of the layered oxide superconductor Sr sub 2 RuO sub 4 , the layered organic superconductor kappa-(BEDT-TTF) sub 2 Cu(NCS) sub 2 and the quasi-two-dimensional Heisenberg antiferromagnet Cs sub 2 CuCl sub 4 , are presented. Chapter 1 introduces the physics of cyclotron resonance in metals and the concepts behind effective mass renormalisation in Fermi Liquid theory. Chapter 2 provides a description of millimetre-wave experimental techniques. Resonant cavity techniques have made it possible to measure the bulk conductivity of anisotropic metallic systems at GHz frequencies. Design details of novel millimetre-wave instruments developed to enable the rotation of a sample in an external magnetic field (i.e. angle-dependence studies) are also provided. Chapter 3 discusses the origin of cyclotron resonance harmonics measured in the high-frequency conductivity of anisotropic metallic systems. These concepts serve as a basis for the interpretation of magneto-optical conductivity measurements in Sr sub 2 RuO sub 4. Chapter 4 presents an angle-dependent study of cyclotron resonance features in the normal state of Sr sub 2 RuO sub 4. A series of harmonic resonance features in the conductivity is observed at odd (n = 3,5,7,9) harmonic multiples of the cyclotron resonance frequency. The features originate from the gamma Fermi surface and the cyclotron mass is m sub c sub r subgamma = 12.35 m sub e. In addition, several resonanc

Gaussian Distribution Approximation for Localized Effects of Input Parameters

In the application of cycle-to-cycle control to manufacturing processes, the model of the process reduces to a gain matrix and a pure delay. For a general multiple input – multiple output process, this matrix shows the degree of influence each input has on each output. For a system of high order, determining this gain matrix requires excessive numbers of experiments to be performed, and thus a simplified, but non-ideal form for the gain matrix must be developed. In this paper, the model takes the form of a Gaussian distribution with experimentally determined standard deviation and scaling coefficients. Discrete die sheet metal forming, a multiple input-multiple output process with high dimensionality, is chosen as a test application. Results of the prediction capabilities of the Gaussian model, as well as those of two previously existing models, are presented. It is shown that the Gaussian distribution model does the best job of predicting the output for a given input. The model’s invariance over a set of different formed parts is also presented. However, as shown in the companion paper on cycle-to-cycle control, the errors inherent in this model will cause non-ideal performance of the resulting control system. However, this model appears to be the best form for this problem, given the limit of minimal experimentation.Singapore-MIT Alliance (SMA

Unconventional cyclotron resonance in Sr2RuO4

An angle-dependent study of the magneto-optical response of the p-wave triplet-paired perovskite superconductor Sr2RuO4\ reveals several new cyclotron resonance effects. We observe an odd-harmonic cyclotron resonance series, probably arising from the gamma Fermi surface, with a fundamental cyclotron mass of 12.6 m(e). In addition, we find several resonance branches which behave in unconventional ways owing to the unusual nature of the band dispersion in this material. The results confirm the complexity of the Sr2RuO4 Fermi surface topology and show that earlier conclusions drawn from millimetre-wave experiments should be reconsidered. (C) 2001 Elsevier Science B.V. All rights reserved

The millimetre-wave magneto-optical response of Sr2RuO4

We report a study of the angle-dependent millimetre-wave magnetoconductivity of the p-wave triplet-paired perovskite superconductor Sr2RuO4. We find two harmonic series. We assign the first to interlayer cyclotron resonance of the beta-Fermi surface and its harmonics, yielding a cyclotron effective mass of m(beta)(cr) = 4.25 m(e). We assign the second series, which contains only odd harmonics, to cyclotron resonance of the gamma-Fermi surface, yielding a cyclotron effective mass of m(gamma)(cr) = 12.4 m(e). In addition, we find a very strong absorption mode in the presence of a magnetic field component parallel to the quasi-two-dimensional (Q2D) planes of the sample. Its dependence on the orientation of the magnetic field cannot be described in the context of conventional Q2D cyclotron resonance, and the origin of this mode is not yet clear

Unconventional cyclotron resonance in the organic superconductor beta''-(ET)(2)SF2CH2CF2SO3

We have measured angle-dependent magnetoresistance oscillations and the interplane millimetre-wave conductivity of the organic superconductor beta "-(ET)(2)SF5CH2CF2SO3 as a function of the orientation of the applied magnetic field. We observe harmonics of the cyclotron frequency in the real-space velocity of quasiparticles orbiting the Fermi surface (FS). The harmonic amplitudes depend on the field orientation, providing a new way to measure the quasi-two-dimensional FS topology